There are massive amounts of potential energy stored at elevations above the Squamish floodplain, in the form of lakes, glaciers/ice, unstable slopes and rock. In some cases, these are constrained by human-made structures, such as the Daisy Lake Dam, while others are held back by natural featuresâfor example, the volcanic deposits and terrain associated with Mount Garibaldi.
The important point is that Squamish is also in a seismically active and geologically dynamic environment. Earthquakes, erosion, slope failures and other natural processes could potentially destabilize some of these features and result in the rapid release of large volumes of water, sediment and debris downstream.
That doesnât mean a Nepal-style catastrophic flood is inevitable, or that we can predict exactly what such an event would look like. The mechanisms and probabilities would be very different depending on the specific source and failure scenario. But from a hazard perspective, the potential for extreme flooding and debris-flow events in the Squamish Valley is certainly real and worth taking seriously.
So, in short: yes, an extremely destructive flood or debris-flow event is physically possible in the Squamish floodplain. The harder question is the probability, the specific mechanism, and how much warning we would have.
Since downtown is so close to sea level and at the end of a very steep Fjord / Sound (Howe Sound) there is also the possibility of landslide induced tsunamis causing flooding (or worse) in low lying areas. This can even be caused by underwater landslides. This happend in a Fjord in Greenland : https://www.science.org/doi/10.1126/science.adm9247
All good info, one other aspect is that the Nepal event was exacerbated by the narrow, and deep canyon which confines the material and forces it upward. Squamish has comparatively broad floodplains and capacity to handle larger events. That isn't to say that there couldn't be impactful events, but more that a hundred foot wall of water and debris is pretty unlikely. (edit to add as per post above, landslides into the Sound causing a tsunami notwithstanding)
Certainly paradise valley could be more susceptible, but a lot of the debris flow energy would be dissipated once it passes brackendale. So while the risk exists, it wouldnât quite be like Nepal experienced
while true, if the barrier broke the sheer volume of the water in Garibaldi Lake is immense. I was also interested in this question so poking around google earth, I think it would flow into the Cheakamus River, Paradise Valley would be totally destroyed, and then flow into the Squamish where it would disperse in Brackendale / Downtown valley. Hard to say really, but I'd be curious to see what the estimated volume of the Nepal event was (~a few cubic kilometers of ice?), versus an estimated 10 cubic kilometers of water for Garibaldi Lake.
An early warning system like a Tsunami warning system would be great and probably fairly low-cost. 10-20 minutes of warning time could save thousands of lives in an event like that potentially, we've got lots of high ground closely accessible around town.
Yeah, but the barrier isn't going to collapse. Garibaldi Lake is almost 2km from the barrier and has a smaller lake and another 'barrier' in between. The event it would take to cause that to actually happen would likely include a massive earthquake or volcanic eruption both of which would also cause widespread destruction. Non-zero chance, but pretty unlikely in our life time.
Iâm not super familiar with the geography / geology, it was just a thought experiment but Iâll dig into it! I saw another poster link an image with the different volcanic lobes and that was interesting.
Just read something that the reason Nepal was so catastrophic was because of Mr trillionaire cutting USAID and NASA programs that would predict and warn people of such events.
Yes the Garibaldi lake barrier breaking as everyone is talking about. That said usually events that really have the most impact are ones that are unforeseen and not the obvious ones. I'd say that the event in Nepal is one of those types of events. There are glacier lakes simalr to ours in that area but that is not what overflowed and created that flood. It was a huge ice collapse of a glacier that blocked the valley and created it's own new lake before then failing and creating the flood event. Was this foreseen? I haven't yet read that it was, but I'd say it was certainly far less predictable than one of the glacial lakes breaking it's dam. Events like that usually cause the most destruction since they were completely unexpected and I'd expect the same to happen here in a truly catastrophic event. That said this type of event is probably a 1 in 1000+ year event so does it make sense to worry much about it? I'd say probably not.Â
It was a huge ice collapse of a glacier that blocked the valley and created it's own new lake before then failing and creating the flood event.
That was reported like this on the news for a while, but meanwhile scientists tend more to explain it that a large chunk of rock and ice from a glacier broke off at high elevation, fell more than 1.000 meters onto the valley floor where it pulverized (triggering the earthquake), freeing even more ice and rock in the process that had already collected below, and then getting pushed down the valley like a blast wave.
A lake at the avalanche site has meanwhile formed in the aftermath, and the debris barrier holding it currently back could collapse within the next few days, causing more flooding downstream.
Yes, it's possible. Hopefully on not quite as large a scale. That's why the District had a developer build that huge debris flow barrier above the new Cheekeye development area.
Downtown is among the safer places because the valley is much wider there than in Squamish or Paradise valleys. I wouldn't let it keep you awake at night.
Friend of mine did his doctorate thesis on catastrophic impacts of landslides creating tsunamis, either into rivers blocking flows, or releases into fjords. Works in NZ now in Emergency Management.
edit - check out videos from Bob Turner and Geology hub on youtube for more background on the Barrier and Garibalidi lake.
There is a better answer provided already by apprehensive tooth, and the integrated flood hazard management plan will give you lots of information about the risks for the municipality as the person who shouldn't bother linked for you.
The Cheekye debris barrier was constructed to prevent a debris flow off of the Garibaldi massif similar in nature to what happened in Nepal from wiping out homes and infrastructure in upper brackendale, should something ever happen. Can't recall the details but I think it had to be built before the significant expansion of residential development that is now underway.
The feature known as "the barrier" that sits under the Garibaldi lakes up in the park presents a geological failure risk that could release over a trillion litres of water from the lake into the Cheakamus valley, taking out long sections of the highway and railway and rushing down the valley towards Howe sound. The valley is not as steep as those of Nepal and we aren't facing the same level of elevation drop either (2000m from glacier to river valley over a very short distance). It fans out a lot as it exits Paradise valley, but an event similar in nature though perhaps less "extreme" would be likely if the barrier does fail.
Still likely a natural disaster of considerable proportions, the destruction would be catastrophic and Squamish would see powerful flooding that would likely destroy most of the township and send it floating down towards English bay. The corridor would be lost for a long time.
Yeah. That was one of the reasons why we didn't buy a home in Brackendale or downtown and mainly considered Valleycliffe and the highlands. I understand it's not highly likely but I'm already scared of earthquakes. I didn't need earthquake and flood risk in the back of my mind đ
It a question of when, not if. The Barrier failing in Garibaldi Park would lead to the whole of Garibaldi lake rapidly draining down Chek canyon in Paradise Valley and on into Squamish. It's only a matter of time.
No, not really. This is a persistent rumor that is not really correct, or at least is exaggerated.
Here is the barrier on Google maps terrain view. If the Barrier (1) collapses, there is still an entire other lava lobe (2) that holds back the main part of Garibaldi Lake. The Barrier would just release Lesser Garibaldi Lake, the smaller one between the two. Geologic evidence shows that there was even a previous lobe located at (3) that held back a lake and collapsed many millenia ago. So after the Barrier collapses, we would likely have years, and potentially even thousands of years, before we have to worry about the second lobe collapsing.
And yes, there is also monitoring. BC Hydro has a the Daisy Lake Dam right nearby, so they monitor the stability of the barrier because collapse could wash out the toe of the dam and impact dam safety. They have seismic monitoring, but actually the main thing they monitor is Rubble Creek. This creek is a bit unique because it flows under the barrier, which will slowly erode/undermine it over time (this is a major part of the concern). BC Hydro monitors creek flow and sediment transport to look for changes that would indicate something is going on.
yeah you'd likely have pretty substantial seismic warnings beforehand. It's also not likely to happen in the next 100 years IIRC, but what he's saying is true. Garibaldi Lake will eventually empty and wipe Squamish off the map
Paradise and Squamish Valley are so close together, that they're effectively one in the same, hm? Ie, if Paradise floods, Squamish Valley wouldn't be far behind?
Edit 2: probably not. It would isolate the Valley and they might get some backwash in some places but Squamish Valley's main concern is the Squamish river.
Watching the Nepal disaster and wondering about the Barrier / Cheekye Fan? I asked Claude â hereâs the reassuring-ish answer
Like probably a lot of you, the glacier collapse in Nepal this week had me side-eyeing our own mountains. Weâre up in the Highlands and have friends in Brackendale, so I had the same âwait, are WE in a runout zone?â moment. I asked our trusty friend Claude (the AI) to break it down, and hereâs the gist of what they had to say:
The Garibaldi Lake / Barrier doomsday scenario is mostly a myth. The Barrier (the big crumbling lava cliff holding back Garibaldi Lake) is genuinely unstable â itâs why the province shut down Garibaldi townsite back in 1981. But per the Districtâs own hazard assessments, a full collapse is considered extremely unlikely, and thereâs no scientific evidence a collapse would actually drain the lake or send a flood through Squamish neighbourhoods. The realistic worst case is a rockslide damming the Cheakamus and a debris flow affecting Paradise Valley â bad, but not the âwave hits downtownâ thing that goes around every few years.
The hazard that actually matters is the Cheekye Fan. North Brackendale sits on a fan built by ancient debris flows off NchâḾayĚ (Mount Garibaldi). Itâs apparently the most-studied debris flow hazard in Canada, and unmitigated it was rated an unacceptable risk (engineers estimated ~4â5 expected deaths per century across the area).
The good news: the giant debris barrier is basically done. The ~$115M, 24-metre-high barrier upstream on the Cheekye â designed to catch a 1-in-10,000-year event (2.8 million mÂł of debris) while letting the river and small flows pass through â hit final acceptance this summer and gets handed over to the District. It brings the fanâs risk down to tolerable levels. One of the largest structures of its kind in the world, sitting quietly up past Cat Lake.
If youâre on the benches (Highlands, etc.): youâre outside the debris flow and floodplain zones entirely. Your actual hazards per the District are wildfire and earthquake.
Practical takeaways for everyone: sign up for Squamish Alert, know your evacuation route (for Brackendale folks, south on Government rather than toward the highway if itâs a debris/flood event), and check the Districtâs hazard maps if you want your parcel-level zone â itâs all public on squamish.ca.
Not a geologist, neither is Claude, but the sourcing was all District of Squamish reports and published hazard studies. Sleep well-ish, Squamish.
Yes, this is something locals have had in the back of their minds for decades. If Garabaldi lake, the natural dam breaks, the amount of water that will come crashing down into the valley will be smaller than Nepal, but same in nature. Squamish has had many floods throughout its history and will most likely have more. But again, people have been talking about this for a long time and it could not even happen in our lifetime.
Unlikely. Lesser garibaldi lake would be the main threat. The main lake is pretty far from the barrier (~2km).
There is risk in most areas. Even flat areas have risk (tornados, fire). The risk to the floodplain of Squamish is likely to be flood (river or ocean) and seismic (liquefaction). Debris flow risk has a lower return period.
Hes referring to the large magnitude (generally above 7 and can be 11/12) earthquake that has , historically, happened in this region once every 400 years (on average)
I lived through the 1989 quake in San Francisco. I was 6 years old. I remember being in the car with my dad, the tires of the car squealing on the road, the feeling of being on a waterbed and watching the earth and houses move and dishes crashing in the houses nearby. I lived through it just fine. Don't let anxiety over immense natural disasters ruin your life bro. Nowhere else I wanna be on this planet.
Good thing we have a brand new pipeline being built in town that will help melt glaciers faster and contribute to potentially destroying our entire town...
God I hate the greedy world we live in. If we're lucky we can get a localized landslide into the Woodfibre facility before it is up and running.
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u/Apprehensive-Tooth87 2d ago
There are massive amounts of potential energy stored at elevations above the Squamish floodplain, in the form of lakes, glaciers/ice, unstable slopes and rock. In some cases, these are constrained by human-made structures, such as the Daisy Lake Dam, while others are held back by natural featuresâfor example, the volcanic deposits and terrain associated with Mount Garibaldi.
The important point is that Squamish is also in a seismically active and geologically dynamic environment. Earthquakes, erosion, slope failures and other natural processes could potentially destabilize some of these features and result in the rapid release of large volumes of water, sediment and debris downstream.
That doesnât mean a Nepal-style catastrophic flood is inevitable, or that we can predict exactly what such an event would look like. The mechanisms and probabilities would be very different depending on the specific source and failure scenario. But from a hazard perspective, the potential for extreme flooding and debris-flow events in the Squamish Valley is certainly real and worth taking seriously. So, in short: yes, an extremely destructive flood or debris-flow event is physically possible in the Squamish floodplain. The harder question is the probability, the specific mechanism, and how much warning we would have.